Add milestone creation and editing

ios/Sources/ContentScreens.swift

@@ -375,9 +375,28 @@ final class MilestonesViewController: RefreshingTableViewController {
         tableView.register(MilestoneCell.self, forCellReuseIdentifier: "milestone")
         tableView.rowHeight = UITableView.automaticDimension
         tableView.estimatedRowHeight = 118
+        let addButton = UIBarButtonItem(
+            barButtonSystemItem: .add,
+            target: self,
+            action: #selector(createMilestone)
+        )
+        addButton.accessibilityLabel = "New milestone"
+        navigationItem.rightBarButtonItem = addButton
         loadContent(refreshing: false)
     }
 
+    @objc private func createMilestone() {
+        let editor = MilestoneEditorViewController(
+            context: context,
+            owner: owner,
+            repository: repository
+        ) { [weak self] _ in
+            guard let self else { return }
+            self.dismiss(animated: true) { self.loadContent(refreshing: false) }
+        }
+        present(UINavigationController(rootViewController: editor), animated: true)
+    }
+
     override func loadContent(refreshing: Bool) {
         loadPage(1, refreshing: refreshing)
     }
@@ -476,9 +495,30 @@ final class MilestoneViewController: RefreshingTableViewController {
         tableView.register(IssueCell.self, forCellReuseIdentifier: "issue")
         tableView.rowHeight = UITableView.automaticDimension
         tableView.estimatedRowHeight = 118
+        let editButton = UIBarButtonItem(
+            image: context.symbol("pencil"),
+            style: .plain,
+            target: self,
+            action: #selector(editMilestone)
+        )
+        editButton.accessibilityLabel = "Edit milestone"
+        navigationItem.rightBarButtonItem = editButton
         loadContent(refreshing: false)
     }
 
+    @objc private func editMilestone() {
+        let editor = MilestoneEditorViewController(
+            context: context,
+            owner: owner,
+            repository: repository,
+            id: id
+        ) { [weak self] _ in
+            guard let self else { return }
+            self.dismiss(animated: true) { self.loadContent(refreshing: false) }
+        }
+        present(UINavigationController(rootViewController: editor), animated: true)
+    }
+
     override func loadContent(refreshing: Bool) {
         loadPage(1, refreshing: refreshing)
     }